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http://dx.doi.org/10.2147/JPR.S71344

Proinflammatory cytokines and DHEA-S in women with fibromyalgia: impact of psychological distress and menopausal status

John A Sturgeon1

Beth D Darnall1

Heather L Zwickey2

lisa J Wood3

Douglas A Hanes2

David T Zava4

Sean C Mackey1

1Stanford University School of Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Palo Alto, CA, USA; 2Helfgott Research Institute, National College of Natural Medicine, Portland, OR, USA; 3Mgh Institute of Health Professions, Boston, MA, USA; 4ZRT Laboratories, Beaverton, OR, USA

Correspondence: John A Sturgeon Stanford University School of Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Stanford Systems Neuroscience and Pain Laboratory, 1070 Arastradero, Suite 200, MC 5596, Palo Alto, CA 94304, USA email jasturge@stanford.edu

Abstract: Though fibromyalgia is not traditionally considered an inflammatory disorder, evi-

dence for elevated inflammatory processes has been noted in this disorder in multiple studies.

Support for inflammatory markers in fibromyalgia has been somewhat equivocal to date,

potentially due to inattention to salient patient characteristics that may affect inflammation,

such as psychiatric distress and aging milestones like menopause. The current study examined

the relationships between proinflammatory cytokines and hormone levels, pain intensity, and

psychological distress in a sample of 34 premenopausal and postmenopausal women with

fibromyalgia. Our results indicated significant relationships between interleukin-8 and ratings

of pain catastrophizing (r=0.555, P,0.05), pain anxiety (r=0.559, P,0.05), and depression

(r=0.551, P,0.05) for postmenopausal women but not premenopausal women (r,0.20 in

all cases). Consistent with previous studies, ratios of interleukin-6 to interleukin-10 were

significantly lower in individuals with greater levels of depressive symptoms (r=−0.239,

P,0.05). Contrary to previous research, however, dehydroepiandrosterone sulfate did not

correlate with pain intensity or psychological or biological variables. The results of the current

study highlight the importance of psychological functioning and milestones of aging in the

examination of inflammatory processes in fibromyalgia.

Keywords: fibromyalgia, cytokines, psychological distress, inflammation

IntroductionFibromyalgia (FM) is a chronic pain disorder that is characterized by widespread bodily

pain with a prevalence of 2% of the US population.1 FM is characterized by wide-

spread bodily pain for at least 3 months that is accompanied by significant complaints

of fatigue, sleep disturbance, and cognitive symptoms,2 and also shows comorbidity

with other somatic complaints, including headaches and gastrointestinal pain.3 As

these symptoms overlap with other somatic disorders like chronic fatigue syndrome

and irritable bowel syndrome, it has been suggested that FM should be defined more

broadly as a somatic distress disorder consisting of multiple physical symptoms, rather

than strictly a chronic pain disorder.4

Inflammatory processes in FMGiven the diverse nature of FM symptoms, evidence suggests a complex etiology

underlying FM. Researchers have proposed several potential mechanisms of FM

symptoms, including central nervous system sensitization,5 sleep disturbance,6 affective

dysregulation,7 and genetic abnormalities.8 Although FM is not commonly defined as an

inflammatory disorder, studies have identified potential abnormalities in inflammatory

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Sturgeon et al

processes that may be contributory factors to FM.9 Indeed,

at a minimum, these findings suggest that there are likely to

be subclinical elevations in inflammation in this syndrome.10

Typically, proinflammatory cytokines are released as part of

an acute-phase response to an inflammatory stimulus and

are centrally involved as mediators of immune responses.11

Elevated levels of circulating inflammatory cytokines and

chemokines, small cytokines involved in chemotaxis, have

been reported by various researchers in studies of individu-

als with FM, including interleukin (IL)-6, IL-8, IL-10, and

tumor necrosis factor-α (TNF-α).

IL-6, a proinflammatory cytokine related to major

depression and various symptoms characteristic of FM

(including hyperalgesia, fatigue, and depression), has been

correlated with pain levels in some pain populations.12 IL-8

is a proinflammatory chemokine involved in increased noci-

ceptive sensitivity and promotion of sympathetic pain,13,14

as well as major depression.15 Results from a recent meta-

analysis16 suggest that proinflammatory IL-6 and IL-8 are

cytokines most commonly elevated in individuals with FM.

The proinflammatory cytokine TNF-α, which is typically

involved in acute-phase inflammation, has also been found

in higher serum levels in individuals with FM.17 Additionally,

elevations of IL-10, a cytokine involved in the regulation of

inflammatory processes that is typically closely associated

with IL-6, have been reported in some individuals with FM

without accompanying elevations in IL-6 in FM.18 Evidence

regarding IL-10 and TNF-α in FM is somewhat less robust,

though the presence of these markers in the literature war-

rants their inclusion in future studies.

In addition to cytokine dysregulation, there may be

hormonal differences that underlie inflammatory processes

in FM. Dysregulation of dehydroepiandrosterone sulfate

(DHEA-S), an endogenous steroid hormone, may play an

etiologic role in the maintenance of FM symptomatology, as

it modulates inflammatory responses through direct inhibition

of IL-6 and TNF-α activity19 and indirectly through promo-

tion of IL-10 release.20 The normative decline of DHEA-S

levels with age has been theoretically linked with the onset

of FM symptomatology across the life span.21

Psychiatric distress and FMHigh levels of psychiatric distress are common in FM;

some estimates suggest a lifetime prevalence of major

depressive disorder in this population as high as 68%, as

well as elevated rates of anxiety.22 The psychological dis-

tress common in FM is an important consideration when

profiling cytokine activity, as this distress has implications

for inflammatory processes. Researchers have identified a

link between major depression and inflammatory markers

like IL-615 and TNF-α,12 as well as less robust relationships

with IL-812,23 and DHEA-S.14,24,25 Further, these cytokines

may have overlapping contributions to inflammatory pro-

files; Dhabhar et al26 reported that individuals with major

depression also demonstrate an increased ratio of serum IL-6

levels to serum IL-10 levels, which may be an etiological

contributor to depression-related inflammatory dysregula-

tion. There is also evidence of increased levels of IL-6,27

IL-10, and TNF-α in certain anxiety disorders. Similarly, an

inverse relationship between DHEA-S and anxiety has been

demonstrated in some populations,28 though the evidence for

this relationship is largely correlational. Further, the relation-

ship between DHEA-S and anxiety may vary significantly

by sex28 and by age.29 To date, few studies have examined

inflammatory processes in FM with specific consideration

for psychiatric distress, but psychological factors are likely a

key factor in further characterizing the relationship between

FM and cytokine levels.

Effects of aging on FM symptomatologyCytokine and chemokine differences underlying FM must

also be examined within the framework of human aging, as

the prevalence of FM increases in older populations,30 and

inflammatory responses change as a function of the normal

aging process.16,17 It is thought that age-related changes in

inflammation are mediated by changes in immune function.31

Although aging is well established as a predictor of inflam-

matory changes in healthy populations, there is a paucity

of research examining age-related differences in cytokine

activity in FM. Studies suggest that IL-6, IL-8, and TNF-α

increase with age,32–34 particularly when accompanied by

significant life stress.32,33 Similarly, DHEA-S levels have

been found to decline as a normal function of aging.35 The

extant literature also suggests the presence of sex differences

in cytokine production, attributable in part to hormonal dif-

ferences between men and women.36 As previous studies

have found differential rates of production of cytokines from

human T-cells and monocytes that vary according to both

age and sex,37 these factors likely have coexisting effects on

immune function and cytokine production and must both be

acknowledged.

One salient factor that is relevant to female-specific

aging and cytokine production is menopause. Menopause

is a key biologic milestone that may underlie age-related

cytokine changes in women with FM, as researchers

have noted an increased rate of early menopause and

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Proinflammatory cytokines and DHEA-S in women with fibromyalgia

hysterectomies in women with FM and have suggested that

these factors may contribute to the development of FM.38

Others have noted that FM symptomatology may initiate

or worsen at the onset of menopause.8 The mechanisms by

which menopause may cause or exacerbate FM symptoms

have not been clearly demonstrated. However, postmeno-

pausal women with FM have demonstrated decreased

circulating levels of some hormones implicated in the

regulation of inflammatory responses, which have been

associated with greater serum levels of IL-6 and IL-8 in

these individuals.39 There is also evidence of a decline in

DHEA-S levels in the years leading up to menopause,40,41

suggesting a contribution of aging factors that are unique to

women. As menopausal status and psychiatric distress may

contribute differentially to inflammatory processes in FM,

the current study aimed to provide preliminary evidence

regarding contributions of these variables to inflammatory

markers and FM-related pain.

Hypotheses of the current studyThe current study proposed to characterize cytokine activ-

ity in FM with a greater focus on the potential psycho-

logical and biologic contributors underlying this disorder.

The current study utilized a subsample of women with

FM from a larger study of cytokine reactivity in FM and

chronic musculoskeletal pain. We sampled baseline serum

cytokine levels (IL-6, IL-8, IL-10, and TNF-α), as well

as DHEA-S levels, in pre- and postmenopausal women

diagnosed with FM. We aimed to characterize all serum

analytes and hypothesized that 1) cytokine and DHEA-S

levels would vary significantly as a function of menopausal

status; 2) there would be significant relationships between

measures of depressive symptoms, pain-specific anxiety,

and pain catastrophizing and all serum analytes; and 3) there

would be a specific effect of depression on the ratio of serum

IL-6/serum IL-10 levels.

MethodsParticipantsThirty-four women were recruited through the Oregon

Health and Science University, Portland, OR, USA, as

part of an experimental study of cytokine responses to a

negative imaginal focus induction. The current manuscript

describes only the basal profiles of the FM participants.

Twenty-one women reported having completed menopause

and 13 reported being premenopause. Due to aberrantly

high levels of IL-6, one postmenopausal participant was

identified as an outlier and was excluded from analyses

involving IL-6. The overall sample was a mean age of 50.3

years (standard deviation [SD] =12.1); premenopausal

participants were a mean age of 37.8 years (SD =6.4), and

postmenopausal women were a mean age of 58.3 years

(SD =6.2). The sample was predominantly Caucasian

(N=30). All premenopausal participants were in the folli-

cular stage of their menstrual cycle when their lab visit was

conducted. FM diagnosis was confirmed through review of

copies of participants’ medical charts. All postmenopausal

women in the current sample underwent natural menopause,

rather than surgically induced menopause. Menopausal sta-

tus was determined by participants’ self-reports regarding

the cessation of their menstrual cycles; participants were

asked how long they had been postmenopausal for, and only

those women who reported being postmenopausal for at

least 1 year were included in the study. Further, we supple-

mented participant self-report of menopausal status with

baseline sex steroid testing (data not shown). Inclusionary

and exclusionary criteria can be found in Table 1. The

Beck Depression Inventory-Second Version (BDI-II)42 was

used to identify participants with current and severe major

depression at the screening session. Participants with active

suicidality or a BDI-II score .35 were excluded from the

current study.

MeasuresDepressive symptomsThe Center for Epidemiologic Studies Scale-Depression

(CES-D) is a commonly used self-report scale that is used

to assess subjective symptoms of depression in research

studies.43 The CES-D contains 20 items, coded 0 (“rarely or

none of the time, less than 1 day per week”) to 4 (“most or

Table 1 Inclusionary/exclusionary criteria

Inclusionary criteria Exclusionary criteria

Women between the ages of 18 and 70 yearsDiagnosed fibromyalgia confirmed by review of medical recordsNonsmokersPremenopausal women must have a normal menstrual cycle

Active or recent virus/infectionPsychosis or active suicidalitycurrent severe major depression (BDI-II score .35)Former intravenous drug userActive corticosteroid regimenNeedle/blood/injection phobiaSex-steroid dysregulationSelf-reported pregnancyTaking β-blockersTaking oral contraception or hormone therapyInflammatory disease (such as lupus)

Abbreviation: BDI-II, Beck Depression Inventory-Second Version.

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all of the time, 5–7 days per week”), with higher numerical

responses corresponding to the greatest intensity of each

depressive symptom. Participant responses are summed, up

to a maximum total of 80. A cutoff score of either 1944 or 2045

has been suggested to reflect clinically significant depression

in chronic pain populations.

Pain-related anxietyParticipants were administered the Pain Anxiety Symptoms

Scale 40-Item Version (PASS-40).46 This questionnaire

assesses domains of cognitive anxiety, pain-related fear,

escape and avoidance responses, and physiological anxiety

using 20 items on a 6-point scale, from 0 (“never”) to 5

(“always”).47 The PASS-40 has demonstrated adequate psy-

chometric properties in clinical pain populations.47

Pain catastrophizingParticipants were administered the Pain Catastrophizing

Scale (PCS),48 which assesses trait levels of catastrophic

thoughts about pain and has demonstrated a reliable fac-

tor structure in a variety of studies.49–51 The PCS contains

13 items, coded from 0 (“not at all”) to 4 (“all the time”),

and summed for a total score from 0 to 52.

Pain intensityPain intensity was assessed using an 11-point visual analog

scale (VAS), with scores from 0 (“no pain at all”) to 10

(“worst pain imaginable”). VAS scales are a common method

of assessment for pain intensity in chronic pain populations

and have demonstrated validity for this purpose.52

ProcedureStudy visit schedulingTo minimize hormonal variability, premenopausal partici-

pants called the study coordinator at onset of menses, and

the study visit was scheduled to occur during the follicular

phase, within days 3–9 of their cycle. The follicular phase was

chosen because it follows the menstrual period and is easy

to predict in our sample of normally menstruating women

by using a calendar. Study visits were scheduled ad libitum

for postmenopausal participants.

Study visit proceduresParticipants in the current study received $150 compensation

for their participation in a larger study that involved 6 hours in

the laboratory and a stress experiment. All participants arrived

at the study site at 8 am, fasting since dinner the night before,

having consumed only water and no caffeine that morning

and having taken medications as prescribed. Participants

completed study questionnaires and were measured for

height, weight, and blood pressure. A topical anesthetic was

offered prior to the placement of an intravenous catheter

(22-gauge or 20-gauge) in the nondominant arm or hand.

Following a 25-minute rest period, blood was drawn into

two 10 mL Vacutainers (Becton, Dickinson and Company,

Franklin Lakes, NJ, USA). Whole blood was immediately

spun and aliquotted, and serum was stored at −80°C until the

assays were performed. Serum levels of TNF-α, IL-6, IL-8,

and IL-10 were measured in duplicate using a bead-based,

high-sensitivity immunofluorescence assay according to

the manufacturer’s instructions (Millipore Inc.). Data were

collected and analyzed using the Luminex 200 system Ver-

sion 2.3 (Luminex, Austin, TX, USA). A four-parameter

regression formula was used to calculate the sample concen-

trations from the standard curves. The threshold for detection

for all analytes was 0.13 pg/mL.

DHEA-S levels were sampled using an enzyme-linked

immunosorbent assay (ELISA).53 At baseline, whole blood

was collected in a sodium heparin tube, and an L1000 pipette

set at 75 µL was used to pipette blood spots onto filter paper.

After drying, blood-spotted filter paper was individually

stored in tightly sealed plastic bags with several desiccant

packets at −80°C. DHEA-S was measured by a serum-based

solid-phase ELISA according to the manufacturer (DRG

EIA-1562) and modified for dried blood spots as described.53

Blood spot levels for DHEA-S correlate well with matched

serum (r=0.89). Intra-assay coefficients of variation for the

dried blood spot DHEA-S assay are 11.2% at 38 µg/dL, 5.0%

at 126 µg/dL, and 12.9% at 244 µg/dL. Interassay coefficients

of variation are 10.8% at 58 µg/dL, 4.4% at 113 µg/dL, and

7.8% at 260 µg/dL. The mean recovery is 104%. The ZRT

Laboratory assay range (20–80 percentile) for women aged

15–80 years is 40–290 µg/dL and is age dependent, with

higher values at younger ages and progressively tapering

with age.

Statistical analysisMeans and SDs were calculated for demographic variables

(age, body mass index), psychological variables (PCS,

PASS-40, CES-D), cytokines (IL-6, IL-8, IL-10, TNF-α),

and DHEA-S. All cytokine variables and DHEA-S were log

transformed to address significant non-normality in their

distributions. Demographic differences and psychological

variables can be found in Table 2, and descriptive statistics

can be found in Table 3. Differences between premeno-

pausal and postmenopausal participants were calculated

using between-group t-tests, and relationships between

study variables were tested using Pearson r correlations.

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Proinflammatory cytokines and DHEA-S in women with fibromyalgia

Table 2 Means and standard deviations of demographic and psychological variables in premenopausal and postmenopausal women

Study variable Full sample (N=34)

Premenopausal (N=13)

Postmenopausal (N=21)

Menopausal status t-test

Age (years) 50.32 (12.045) 37.38 (6.36) 58.33 (6.24) t(32) =−9.446, P,0.001BMI (kg/m2) 30.43 (8.08) 31.68 (9.47) 29.69 (7.29) t(30) =0.669, P=0.509CES-D 18.32 (10.90) 19.08 (11.62) 17.86 (10.70) t(32) =0.313, P=0.757Pcs 20.21 (13.44) 27.46 (12.46) 15.71 (12.22) t(32) =2.703, P=0.011PASS-40 71.38 (37.73) 86.39 (42.99) 62.10 (31.67) t(32) =1.895, P=0.067

Abbreviations: BMI, body mass index; CES-D, Center for Epidemiologic Studies Scale-Depression; PCS, Pain Catastrophizing Scale; PASS-40, Pain Anxiety Symptoms Scale 40-Item Version.

Correlations between study variables in pre-menopausal

women can be found in Table 4, and correlations between

study variables in post-menopausal women can be found in

Table 5. Moderation of relationships between psychological

and cytokine measures was tested, when appropriate, by the

interaction between menopausal status and the psychological

predictor (eg, CES-D scores) in an analysis of covariance

model. All analyses were conducted using SPSS Version 20

(IBM Corporation, Armonk, NY, USA). The correlations

reported in the results section are presented with probabil-

ity values that are not adjusted for multiple comparisons

between variables. Given the small sample size and the

prevailing goal adopted by the current study of identifying

associations for future study, this was deemed an appropri-

ate step for characterizing the potential relationships of

substantive interest.

ResultsStudy demographicsParticipants in the current study showed comparable lev-

els of pain anxiety as previous studies of healthy women

(mean [M] =54.82, SD =27.53 in the Osman et al54 study)

and individuals with FM and chronic low back pain (mean

scores ranging from 68.4 to 84.7 in the Roelofs et al55 study).

Participants in the current study showed higher scores on

the CES-D than healthy women in a community sample

(M=10.4, SD =10.3 in the Frerichs et al56 study) but com-

parable CES-D scores were also comparable with previous

samples of individuals with FM (M=17.29, SD =9.39 in the

Giesecke et al57 study). PCS scores in the current sample

were also generally comparable with scores in healthy

women from a community sample (M=15.68, SD =10.93

in the Osman et al50 study) and in samples of women with

chronic pain (M=24.29, SD =8.75 in the Osman et al50 study).

Notably, however, PCS scores were significantly higher in

premenopausal than postmenopausal participants in our study

(t[32] =2.703, P=0.011).

Menopausal status and biological variablesDHEA-S levels did not differ significantly according to

menopausal status. Regarding cytokine and chemokine dif-

ferences, some statistically significant differences were noted

according to menopausal status. TNF-α was significantly

higher in postmenopausal women (t[31] =−2.873, P=0.007).

Serum IL-8 levels did not significantly differ by menopausal

status, though a trend toward higher IL-8 levels in postmeno-

pausal women was detected (t[31] =−1.75, P=0.090). There

were no menopausal status-based differences noted in levels

of IL-6, IL-10, or IL-6/IL-10 ratios that reached statistical

significance (P.0.10 in all cases).

Relationships between biologic variables and psychological variablesIL-8 correlated significantly with CES-D scores in the over-

all sample (r=0.363, P=0.038), but not with PCS (r=0.200,

P=0.264) or PASS-40 scores (r=0.238, P=0.183). Significant

Table 3 Means and standard deviations of log-transformed biological variables in premenopausal and postmenopausal women

Study variable Full sample (N=34)

Premenopausal (N=13)

Postmenopausal (N=21)

Menopausal status t-test

IL-6 2.94 (2.57) 3.60 (3.29) 2.48 (1.91) t(31) =−0.044, P=0.965IL-8 7.63 (4.80) 5.86 (2.84) 8.79 (5.50) t(31) =−1.748, P=0.090IL-10 25.71 (55.65) 31.41 (52.40) 22.01 (59.70) t(31) =0.943, P=0.353IL-6/IL-10 ratio 0.75 (2.08) 0.43 (0.77) 0.96 (2.60) t(31) =−1.424, P=0.164TNF-α 11.66 (6.96) 8.33 (4.11) 13.83 (7.64) t(31) =−2.873, P=0.007DHEA-S 5.94 (5.67) 8.24 (6.81) 4.74 (4.72) t(30) =1.705, P=0.099

Notes: All biological variables were log transformed to address non-normality. One participant’s data for IL-6 were excluded due to abnormally high scores.Abbreviations: IL, interleukin; TNF-α, tumor necrosis factor-α; DHEA-S, dehydroepiandrosterone sulfate.

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Table 4 Correlations between biologic variables in premenopausal women (N=13)

Study variable IL-6 IL-8 IL-10 TNF-α DHEA-S PCS PASS-40 CES-D Pain intensity

IL-6 1 0.302 0.526† 0.443 −0.391 −0.106 −0.107 −0.027 0.284IL-8 1 0.346 0.046 0.461 −0.153 0.131 0.173 0.423IL-10 1 0.488† −0.075 0.370 0.327 0.379 0.648*

TNF-α 1 0.133 0.409 0.300 0.237 0.370DHEA-S 1 −0.019 0.164 0.257 0.280Pcs 1 0.851** 0.542† 0.237PASS-40 1 0.788** 0.472CES-D 1 0.790**Pain intensity 1

Notes: †P,0.10; *P,0.05; **P,0.01. All cytokine variables (IL-6, IL-8, IL-10, TNF-α) were log transformed to address non-normality.Abbreviations: IL, interleukin; TNF-α, tumor necrosis factor-α; DHEA-S, dehydroepiandrosterone sulfate; PCS, Pain Catastrophizing Scale; PASS-40, Pain Anxiety Symptoms Scale 40-Item Version; CES-D, Center for Epidemiologic Studies Scale-Depression.

Table 5 Correlations between biologic variables in postmenopausal women (N=21)

Study variable IL-6 IL-8 IL-10 TNF-α DHEA-S PCS PASS-40 CES-D Pain intensity

IL-6 1 −0.084 0.367 0.266 0.066 −0.051 −0.045 −0.133 −0.494*IL-8 1 0.140 0.381† 0.187 0.555* 0.559* 0.551* 0.696**IL-10 1 0.692** −0.207 0.073 0.010 0.071 0.013

TNF-α 1 −0.184 0.234 0.236 0.215 0.035DHEA-S 1 0.405† 0.187 −0.027 −0.355Pcs 1 0.830** 0.613** 0.160PASS-40 1 0.715** 0.288CES-D 1 0.451*Pain intensity 1

Notes: †P,0.10; *P,0.05; **P,0.01. All cytokine variables (IL-6, IL-8, IL-10, TNF-α) were log transformed to address non-normality.Abbreviations: IL, interleukin; TNF-α, tumor necrosis factor-α; DHEA-S, dehydroepiandrosterone sulfate; PCS, Pain Catastrophizing Scale; PASS-40, Pain Anxiety Symptoms Scale 40-Item Version; CES-D, Center for Epidemiologic Studies Scale-Depression.

and positive correlations were found between IL-8 and all

of the psychological measures for postmenopausal women

only: CES-D (r=0.551, P=0.012), PCS (r=0.555, P=0.011),

and PASS-40 (r=0.559, P=0.010). IL-8 did not correlate with

CES-D (r=0.042, P=0.893), PASS-40 (r=−0.068, P=0.824),

or PCS scores (r=−0.290, P=0.336) in the premenopausal

group. IL-6 and IL-10 levels were uncorrelated with PCS,

PASS-40, or CES-D scores and when examined separately

by menopausal status. Similarly, TNF-α levels were uncor-

related with PCS, PASS-40, and CES-D scores in the overall

participant sample and when tested separately by menopausal

group. DHEA-S levels did not correlate with serum cytokine

or chemokine levels, pain intensity, or PCS, PASS-40, or

CES-D scores in the overall sample or in any subgroup of

participants.

Depression and IL-6/IL-10 ratiosA significant correlation was noted between IL-6/IL-10 ratios

and CES-D scores in the overall sample (r=−0.409, P=0.018),

though this relationship did not reach statistical significance

in either the premenopausal group (r=−0.490, P=0.089) or

the postmenopausal group (r=−0.337, P=0.146). Menopausal

status did not moderate the relationship between CES-D and

IL-6/IL-10 ratios (P.0.50).

DiscussionThe current study aimed to characterize basal cytokine

profiles in pre- and postmenopausal women with FM

through examination of serum concentrations of cytok-

ines, chemokines, and inflammation-regulating hormones.

Further, we sought to provide additional context to these

findings through the examination of other factors that are

likely to be contributory to inflammatory processes, namely

menopausal status and psychological distress. Our findings

revealed interesting differences in inflammatory processes

when the menopausal status and psychological status of

participants were taken into account.

Mean scores on psychological variables in the current

study were comparable with previous samples of chronic pain

using the PCS, CES-D, and PASS-40 scores. Premenopausal

and postmenopausal participants reported similar levels of

depressive symptoms and pain anxiety. Although premeno-

pausal participants did report significantly higher levels of

pain catastrophizing, the average scores on the PCS for these

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Proinflammatory cytokines and DHEA-S in women with fibromyalgia

participants were similar to previous samples of individuals

with FM.58 As noted previously, however, participants in

our study showed somewhat elevated levels of depressive

symptoms compared with community samples of healthy

women, though no obvious differences in pain anxiety or

pain catastrophizing were noted.

Our results suggested that IL-8 was correlated with

depressive symptoms, pain catastrophizing, and pain-related

anxiety for postmenopausal women but not for premeno-

pausal women. These findings suggest a possible contributing

role for IL-8 in psychological functioning in chronic pain,

which is contrary to some previous findings.14,18,59 While pre-

vious work has largely focused on describing inflammatory

factors in isolation, our findings underscore the importance of

considering menopausal status and psychological functioning

in future studies that examine inflammatory processes that

may underlie FM. It is particularly important to acknowledge

the relative scarcity of attention paid to the role of menopause

and other age-related factors in FM, despite evidence that the

prevalence of FM increases as individuals progress further

into old age,30 and that there appear to be changes in brain

structure and function that have age-dependent implications

for individuals with FM.60

Our results suggested no relationship between IL-6 and

measures of psychological distress. While these findings

stand at odds with the broader literature, largely comprising

studies describing healthy samples,10,12 they support previ-

ous findings for FM. A study by Bazzichi et al18 reported

no differences in IL-6 and IL-8 plasma levels between

those with FM and a diagnosed psychiatric disorder like

depression and anxiety and those with FM and no psychi-

atric diagnoses. The reason for this divergence is unclear,

though these f indings may suggest a unique immune

characteristic of FM. Our results do not allow for infer-

ences regarding the specificity of this effect in FM versus

a general effect of the experience of chronic pain, but the

relationship between IL-6 and depression in other chronic

pain disorders warrants further study in the future. Further,

our finding of a significant relationship between depres-

sive symptoms and IL-6/IL-10 ratios replicates previous

research that suggests dysregulation of cytokine activity

in depression.26 We expected that menopausal status would

modify the salience of IL-6/IL-10 ratios in the context of

psychological functioning, but this was not supported by

our findings. This null finding may have been attributable

to a small sample size, however, which will be discussed

later. Additional research of this relationship is therefore

needed in larger samples.

It is notable that DHEA-S levels did not correlate with

pain intensity or cytokine or chemokine levels in our study,

which were somewhat unexpected findings. However, it is

conceivable that DHEA-S plays a more dynamic role in the

regulation of inflammatory responses, as to an acute stressor,

but does not have a detectable relationship in the basal state

with these immune factors. It is also possible that the regula-

tory effects of DHEA-S are too complex to be adequately

characterized using correlations. Previous evidence suggests

that the effects of DHEA-S may be best described in their

relation to cortisol61 and testosterone levels,62 both of which

have implications for immune competence and markers of

inflammation like IL-6 and IL-8, and may be affected by

other underlying medical factors like hypothyroidism63 or

low estrogen.64

The overall literature regarding inflammatory processes

in FM is inconsistent and commonly includes conflicting

results.65 The inconsistency of these effects may be attrib-

uted to variability in measurement and analytic methods,

sample size, and lack of sufficient adjustment for relevant

confounding variables such as physical activity, medical

status, and psychiatric comorbidities.16 Such methodological

and statistical issues limit the interpretability of the extant

literature and highlight the need for greater methodological

rigor and a greater consideration for relevant third variables

in order to characterize inflammatory processes in FM in

the correct context. The current study was intended as a

preliminary attempt to identify salient contributing factors

to inflammatory processes in FM, thereby highlighting the

need to account for these factors in future studies.

LimitationsA primary limitation of the current study is the size of our

sample. As a result, the current study should be considered a

pilot study that was exploratory in nature and was conceived

as an attempt to detect novel associations between the study

variables that could be more stringently examined in future

studies. The limited size of our sample means that our find-

ings require replication in larger samples to ensure that they

are reliable. Our results are similarly limited due to the unbal-

anced size of the groups; conclusions regarding our findings

should be made with caution and with the understanding that

there was a comparatively larger number of postmenopausal

women, which may explain some degree of the difference

in significant relationships between variables in the pre- and

postmenopausal groups. Further, our presented findings do

not provide adjusted significance values that account for the

multiple comparisons posed by our analyses. We deemed

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Sturgeon et al

this approach necessary, given the small size of our sample

and our intention to identify novel effects, but the lack of

adjustment to the presented probability values is nevertheless

a significant limitation. Consequently, our findings should

be interpreted with this caution in mind. Additionally, some

recent evidence suggests that measuring reactivity, rather

than basal levels, of IL-6 may constitute a more reliable mea-

surement approach in individuals with FM.66 As the current

study provided only basal values of IL-6 and other biological

variables, examination of these relationships with regard to

cytokine reactivity is warranted in future studies.

We determined the presence of FM by relying on

participants’ medical records, rather than performing

diagnostic testing to confirm participant diagnoses during

the study. This approach relies on diagnosis from previ-

ous medical providers, which may be variable with regard

to adherence to a strict set of diagnostic criteria for FM.

Though we have no reason to suspect inaccurate FM diag-

noses in our study sample, our results should be interpreted

with this caution in mind. Similarly, the current study did not

specifically target individuals with clinical mood disorders.

It is possible that specific examination of individuals with

diagnosed mood disorders such as major depressive disorder

may demonstrate stronger relationships between distress

and cytokine production if these relationships are examined

according to sex- and age-specific factors, as in the current

study. Due to differences in the processing of sampling

assays compared with previous studies, we were also unable

to provide comparisons with cytokine levels in healthy pre-

and postmenopausal women, which could serve to provide

additional context to our findings and would provide a

clearer illustration of the processes of FM. Although FM is

predominantly found in women, comparison of our findings

with similarly aged men, both with and without FM, would

also be beneficial to delineate the unique aspects of sex,

aging, and inflammatory processes in FM. As a result, we

urge attention to these issues in future studies. Despite these

limitations, we propose that our findings regarding differ-

ential implications of psychological and menopausal status

for IL-6, IL-8, and IL-10 activity should be interpreted as

preliminary findings that warrant further examination with

additional sampling in a larger study in the future.

ConclusionThe current study sought to characterize differences in

basal proinflammatory cytokine profiles in women with

FM. While data are preliminary, the current study is among

the first to present serum cytokine levels in women with

FM, and the first to do so with specific attention paid to

age-related and psychological factors. Our findings regard-

ing the role of menopause are particularly important, as

they highlight the potential importance of aging factors in

understanding the development of FM in women. However,

replication of our results in larger samples of women

with FM is necessary. Our findings highlight an avenue

for future research that may provide additional utility

in characterization of the complex etiology and clinical

presentation of FM.

DisclosureDr Zava is the owner and president of ZRT Laboratories. The

authors report no other conflicts of interest in this work.

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